INSECTS INJURIOUS TO CABBAGE, ETC. 335 



unaffected plants. The wingless females become full grown in 

 about thirteen days during the summer and live for about forty-six 

 days, during which time they will give birth to an average of forty- 

 one young, producing as high as six young in a day. The winged 

 forms are much shorter lived, living only about ten days and giving 

 birth to but from seven to thirteen young. 



There is no question that in the Southern States the viviparous 

 females may continue to reproduce all winter, and it is quite prob- 

 able that some of them survive in pits and cellars in the North, 

 where eggs also probably occur. Thus Sirrine* states that it " is 

 certain that this aphid can survive the winter on cabbage stored 

 in cellars or pits, also that cabbage stored in pits for seed purposes 

 furnishes the supply of aphids for infesting the seed stalks in early 

 spring." This being the case it should be an easy matter to de- 

 stroy the aphids by fumigation before removing them from the pits. 



Control. From the habits outlined it is evident that, as for 

 other cabbage pests, the refuse of the crop should be cleared up and 

 destroyed in the fall. Any of the standard contact insecticides, 

 such as kerosene emulsion, 1 part stock solution to 15 parts of 

 water, whale-oil soap, 1 pound to 6 gallons, or " Black-leaf 40," 

 1 part to 800 of water, will destroy the aphids, but the spray- 

 ing must be thorough, as the waxy coating serves to protect 

 them. According to Professor Franklin Sherman, any good 

 laundry soap used at the rate of 1 pound dissolved in 3 gallons of 

 water, will destroy the aphids. Where water under pressure is 

 available in a small garden, the aphids may be held in check by 

 washing them from the plants with a strong stream from a garden 

 hose. Plants infested in the seed-bed may be freed from the 

 aphis by dipping in whale-oil soap solution, 1 part to 8 of water. 



Fortunately for the grower, the cabbage-aphis is usually held 

 in check by numerous parasitic enemies, principally little wasp- 

 like flies of the family Braconidce, and by several species of lady- 

 bird-beetles and syrphus-fly larvse, which will often destroy a 

 colony within a few days. 



The Spinach-aphis or Green Peach-aphis f 



Another species of aphis often becomes destructive to cabbage, 

 spinach, celery and lettuce, as well as various greenhouse crops 



\F. A. Sirrine, Bulletin 83, N. Y. Agr. Exp. Sta., p. 675. 

 t Myzus persiccB Sulz. 



